The invention relate to a hydraulic steering system for vehicles in which the steering motor is arranged to be supplied with compressed fluid by way of a steering unit adjustable by means of a steering element.
Vehicles which are equipped with such a hydraulic steering system have the advantage that it is only hydraulic lines that require to be arranged between the driver's cab and the wheels to be steered; no mechanical linkage is required. The known steering units, for example of type OSPC manufactured by the Applicant, ensure that an amount of compressed fluid proportional to the angle of rotation of the steering handwheel is supplied to the steering motor. it is also allowed to drive such vehicles to be driven on roads.
It is frequently desirable for the wheels of a vehicle to be adjusted more quickly than corresponds to normal steering operation. This applies, for example to work vehicles such as shovel dredgers, excavators, center-pivot steered vehicles and so on, which are intended to carry out rapid movements at the site of use.